In a network environment, providing proximity based services to a user involves locating users to the nearest access point. By finding the location of devices, whether it be in a wireline or wireless environment from a network standpoint, carriers can provide a whole range of services. Using this framework, carries can allow users to “pull” information from the network as well as “push” information to the network based on a user's current location.
However, to date, there has been difficulty in determining location across a range of network and device types. Location of mobile users via Global Positioning System (GPS) is possible but ineffective in an indoors environment where buildings block GPS transmissions. Access point attachment of mobile devices is another way of determining a mobile user's location, however, this is proprietary in its methods.
One proposed indoor solution is the Microsoft RADAR system. This system uses the RF signal strength in the communications network as an indicator of the distance between a transmitter and a receiver. As a user walks between access points of a WLAN such as in a building, the signal strength varies. The signal received at the device is strongest when the receiver is close to the access point and weakest when the device is far away. A problem with this system is that RF signals scale poorly around walls and other obstructions within a building. RF signal strength is unpredictable in occupied spaces and thus a user may be located close to an access point but the signal strength reading may indicate a far greater distance. Accuracy of the system varies greatly between areas with obstructions and areas without obstructions. The infrastructure of the system, eg RF antennas and the like, greatly adds to the cost of implementing these methods.
A further proposed solution is the AT&T Active BAT system which works by monitoring Ultrasound and RF signals. Wireless devices in the system are tagged by attaching small wireless transmitters. The location of these transmitters is tracked by the receiving elements to determine the location of each wireless device in the building. The BAT system imposes a significant additional infrastructure cost doe to the RF base station, the matrix of receiver elements and wireless transmitters. The time required to build the network is also significant. The network provides little flexibility.